The natural heart, and specifically, the cardiac tissue of the natural heart can fail for various reasons to a point where the natural heart cannot provide sufficient circulation of blood for a body so that life can be maintained. As a solution for the failing natural heart, several attempts have been made in the past to provide a device to maintain circulation.
One such approach has been to either assist or to entirely replace the existing natural heart in a patient with an artificial heart, or to transplant a natural heart from another human into a patient. Several drawbacks have limited use of these devices and transplants to applications of a brief time period. As such, these devices and transplants have a real lasting benefit and use to only a tiny fraction of those afflicted with a failing natural heart.
A particular problem stems from the fact that the materials used for the interior lining of the chambers of an artificial heart are in direct contact with the circulating blood, which can enhance undesirable clotting of the blood, build up of calcium, or otherwise inhibit the blood's normal function. Hence, thromboembolism and hemolysis could occur with greater ease. Additionally, an artificial heart lining can crack, which inhibits performance, even if the crack is at a microscopic level.
The transplant procedure requires removing an existing organ (i.e., the natural heart) for substitution with another organ (i.e., another natural heart) from another human, or potentially, from an animal. Before replacing an existing organ with another, the substitute organ must be "matched" to the recipient, which can be, at best, difficult and time consuming to accomplish. Furthermore, even if the transplanted organ matches the recipient, a risk exists that the recipient's body will reject the transplanted organ and attack it as a foreign object. Moreover, the number of potential donor hearts is far less than the number of patients in need of a transplant. Although use of animal hearts would lessen the problem with fewer donors than recipients, there is an enhanced concern with rejection of the animal heart.
In an effort to use the existing natural heart of a patient, other attempts have been made to wrap skeletal muscle tissue around the natural heart to use as an auxiliary contraction mechanism to pump the natural heart. As currently used, skeletal muscle cannot alone typically provide sufficient and sustained pumping power for maintaining circulation of blood through the circulatory system of the body, especially for those patients with severe heart failure.
Still another concept for maintaining the existing natural heart as the pumping device involves enveloping a substantial portion of the natural heart, such as the entire left and right ventricles, with a pumping device for rhythmic compression. Although somewhat effective as a short term treatment, the pumping device has not been suitable for long term use. Typically, a vacuum pressure is needed to overcome cardiac tissue/wall stiffness so that the chambers can return to their original volume and refill with blood. This "active filling" of the chambers with blood limits the ability of the pumping device to respond to the need for adjustments in the blood volume pumped through the natural heart, and can adversely affect the circulation of blood to the coronary arteries. Natural heart valves are quite sensitive to wall and annular distortion, and movement patterns that reduce a chamber's volume do not necessarily facilitate valve closure (which can lead to valve leakage). Another major obstacle with long term use of such pumping devices is the deleterious effect of extensive mechanical contacting of living internal surfaces (endocardium). In certain cases, this coaptation of endocardium tissue is probably mechanically necessary for a device that encompasses both ventricles to produce independent output pressures, but it can compromise the integrity of the living endothelium.
Another device developed for use with an existing heart for sustaining the circulatory function of a living being and the pumping action of the natural heart is an external bypass system, such as a cardiopulmonary (heart-lung) machine. Typically, bypass devices of this type are complex and large, and, as such, are limited to short term use in an operating room during surgery, or to maintaining the circulation of a patient while awaiting receipt of a transplant heart. The size and complexity effectively prohibit use of bypass systems as a long term solution, as they are rarely even portable devices. Furthermore, long term use of a heart lung machine can damage the blood cells and blood borne products, resulting in post surgical complications such as bleeding, thromboembolism function, and increased risk of infection.
Consequently, none of the previous available techniques or devices for maintaining circulation of blood provided an adequate or practical long-term use device or technique for adequately maintaining sufficient blood pressure and circulation of blood through the circulatory system of the body.